1. Field of the Invention
The present invention pertains to fire control systems, and, more particularly, to alignment of fire control systems.
2. Description of the Related Art
In a fundamental sense, “fire control” refers to the ability to control a weapon system so that one accurately hits a target at which one is firing—typically, with a projectile of some sort. A simple fire control for a simple system—e.g., shooting a firearm—may include merely sighting along the boresight of the weapon. Fire control systems have evolved much higher complexity along with the weapon systems with which they are associated. Consider, for instance, the Aegis combat system found aboard the Ticonderoga-class guided missile cruisers of the United States Navy. The Aegis combat system, according to some sources, is capable of simultaneous anti-air, anti-surface and anti-submarine warfare, including search, tracking, and missile guidance functions simultaneously with a track capacity of over 200 targets at more than 200 miles. In large part, this increase in complexity has arisen from increased automation permitted by rapid growth in powerful computing technology.
Increased complexity typically affords increased opportunity for error. Two kinds of error are “target location error” and “alignment error.” Target location errors are differences between where the weapon system thinks the target is and where it actually is according to an absolute reference. These can arise from such various sources incorrectly reckoning the position to which a moving target will move, errors in data entry, and differences in reference systems between different sources of positioning information. Alignment errors are differences between where the weapon is line of fire actually is and where the line of fire should be.
In a Future Combat Systems (“FCS”) program sponsored by the United States military, an Armed Robotic Vehicle-Assault (Light) (“ARV-A(L)”) vehicle is under development. Weight reduction efforts and integration complexities have forced separation of the gun targeting system from the gun turret so that the gun and targeting system experience a different set of alignment errors. The ARV-A(L) vehicle features the Medium Range Electro Optic Infrared (“MR EO/IR”) targeting sensor system with its internal gimbal mounted directly to a fixed kingpost. The ARV-A (L) also incorporates an XM-307 gun on a separate azimuth rotational system that revolves around the fixed kingpost. In the current design, target states are estimated from MR EO/IR data and fire control uses the MR EO/IR target tracks to develop a fire control solution. Unknown alignment errors between the MR EO/IR sensor and the gun coordinate systems could cause errors in target position and velocity when referenced to the gun coordinate system during firing.
Traditional gun systems have utilized a bore sighting methodology to accurately align the gun and missile systems with the sensor. Bore sighting can be a slow and often repeated process, dependant upon the ability of the system to remain in alignment between bore sighting events. The ARV-A (L), as a 2½ ton to 3 ton class system, will not have the massive and rigid structure traditionally associated with combat vehicles, which will make retention of bore sight alignment much more difficult. Effects of shock and vibration, solar heating, reduced vehicle stiffness through use of light weight materials, and the need to constantly travel over rough terrain will increase the need for bore sighting. On an unmanned vehicle, this is very undesirable, as traditional bore sighting requires at least one man to be involved. A kingpost design further complicates alignment of the sensor to the weapon systems, as two distinct points of azimuth and elevation rotation will exist-one for the sensor, and one for the weapons.
Transfer alignment can be automated and used to align the two azimuth rotation points through the use of inclinometers. The inclinometers could be placed on the sensor and weapons deck base and measurements taken at all 360° of rotation for each of the two rotation points. Differences in angle could be removed via algorithms in the fire control system. This process would eliminate most alignment error between the two azimuth planes, but would not be a complete solution.
The present invention is directed to resolving, or at least reducing, one or all of the problems mentioned above.